1. Field of the Invention
The present invention relates to a chip antenna and, more particularly, to a chip antenna for use in a mobile communication apparatus, such as a PHS (Personal Handy-phone System) or a portable telephone set using the chip antenna.
2. Related Art of the Invention
A print antenna which has a plurality of resonance frequencies and which can be used at a plurality of frequencies at the same time has been proposed in Japanese Unexamined Patent Publication No. 8-186420. FIG. 11 shows a conventional print antenna having a plurality of resonance frequencies, which can be used for two frequencies. A print antenna 50 is formed of a dielectric substrate 52 on which a monopole element 51 whose one end is connected to a power source V is printed. An anti-resonance circuit 54, which is a parallel circuit of a chip inductor 53a and a chip capacitor 53b, is inserted in the intermediate portion of the monopole element 51, and the monopole element 51 is separated into a first antenna element 51a and a second antenna element 51b. The monopole element 51 resonates at a first frequency f1 (wavelength: .lambda.1), and the length of the monopole element 51 at this time is approximately 1/4.lambda.. Also, the anti-resonance circuit 54 resonates at a second frequency f2 (wavelength: .lambda.2). Further, since the first antenna element 51a is made to singly resonate at the second frequency f2, the length thereof is set at approximately 2/4.lambda.. Since the anti-resonance circuit 54 resonates at the second frequency f2, the print antenna constructed as described above becomes equivalent to a state in which with respect to the second frequency f2, the second antenna element 51b is opened, and resonates at the first frequency f1 and also the second frequency f2. Thus, the print antenna has two resonance frequencies.
The band width of the first and second frequencies f1 and f2 is determined by the width of the first and second antenna elements 51a and 51b. An increase in the width makes it possible to increase the band width of the first and second frequencies f1 and f2.
However, according to the above-described conventional print antenna, if an attempt to realize a wider band is made, the width of the first and second antenna elements must be increased, causing the print antenna to become enlarged, as a result, presenting the problem that it is difficult to form the mobile communication apparatus which mounts this print antenna into a smaller size.